1. Field of the Invention
The current invention relates firstly to a device for measuring the injection quantity of injection nozzles for internal combustion engines of motor vehicles and in particular in production testing, which has at least one measuring chamber that is at least partially filled with a testing fluid, a coupling device that can couple at least one injection nozzle to the measuring chamber, a detection device, which detects a state change of the testing fluid in the measuring chamber at least intermittently during an injection by the injection nozzle, and a processing unit, which, based on the signal from the detection device, determines an injection quantity that corresponds to the state change.
2. Description of the Prior Art
A device of this kind is known on the market and is referred to as an injected fuel quantity indicator. This component is comprised of a cylinder in which a piston is guided. The inner chamber of the cylinder and the piston define a measuring chamber. This measuring chamber has an opening against which an injection nozzle can be placed in a pressure-tight manner. When the injection nozzle injects fuel into the measuring chamber, the piston moves, which is detected by a travel sensor. The volume change of the measuring chamber and therefore the injected fuel quantity can be calculated from the distance traveled by the piston.
The known injected fuel quantity indicator, however, has various disadvantages. On the one hand, it has moving parts, which are subject to wear with a continuous use of such a device. This wear is relatively significant because modern injection nozzles are tested not only in random spot checks but also continuously during production. In the course of the service life of such an injected fuel quantity indicator, this wear distorts the measuring results and ends up shortening the service life of the injected fuel quantity indicator.
Moreover, friction is produced between the piston and the cylinder, which hinders the free movement of the piston and results in the fact that the movement of the piston does not fully correspond to the fuel volume actually injected. The measuring precision of the injected fuel quantity indicator is therefore limited. Finally, particularly with injection nozzles for modern diesel engines, it is also necessary to be able to reliably measure very small injection quantities. Measurements of this kind are either difficult or completely impossible with the known injected fuel quantity indicator.
The object of the current invention, therefore, is to modify a device of the type mentioned above so that it can measure the injection quantity of injection nozzles with high precision over its entire service life and can also reliably measure very small injection quantities.
This object is attained by virtue of the fact that the detection device has a capacitor, whose one electrode is comprised of an electrically conductive fluid, which is at least partially contained in a volume connected to the measuring chamber, and the processing unit is connected to the capacitor in such a way that it can detect a change in its capacitance, which is produced by a movement of the electrically conductive fluid.